I am always suspicious of anything that loads/installs with out my consent. Perhaps there was an add on or opt out box in the dictionary add on you did not see. Does something show up in Manage Add Ons that would show this pop up, or give any clues where it came from. It appears that mindspark Interactive Network develops Social Networks. perhaps this came from Facebook or Google+ or such. It is hard to say with further investigation.

McAfee Site Advisor states that it has tested the MindSpark site and found nothing malicous. So, evidently, it is safe. I will see if I can re-download the DictionaryBoss without the MindSpark add-ons.

Though McAfee says that MindSpark is safe, I would not recommend it. I reinstalled DictionaryBoss and MindSpark add-ons come with it, whether you indicate you want it or not. Then, whenever you go on the internet, two Mindspark pop-ups appear in succession. You must permit (Yes) or deny (No) each pop-up before you can begin surfing.